Liquid crystal displays (LCDs) are used extensively as monitors for numerous computer applications. Generally, liquid crystal displays are an assembly comprising a glass panel unit (which is a thin film transistor matrix controlling a liquid crystal emulsion contained between glass plate electrodes); driver electronics which provide the control signals to the thin film transistor matrix, and a lighting unit placed beneath the glass panel unit for illuminating the liquid crystal display panel. The glass panel unit includes a transparent glass substrate upon which the thin film transistor matrix is placed (the LCD or panel substrate), a second conducting transparent glass plate placed a small distance from and parallel to the panel substrate, filled-in between with the liquid crystal material, and sealed around the edges. The second glass panel is also prepared as an electrode to establish a capacitive connection with the individual transistors in the thin film transistor matrix on the panel substrate. The entire assembly is housed by a frame and usually has the driver assemblies attached to the frame near the front surface of the panel substrate which contains the thin film transistor array. The liquid crystal material is subjected to electric fields set up between the transistors and the thin film transistor and the cover glass transparent electrode.
Increasing the size of LCDs is continuously being demanded by industry. One method used to fabricate larger displays is referred to as tiling. In tiling, conventional sized LCD tiles are arranged in a matrix. Typically, the driver chips are interconnected to the LCD either directly on the perimeter of the display or to flexible tape which is then interconnected to the edge of the LCD.
In the tiling method, edges of an individual LCD tile may be internal to the overall matrix edge. However, these internal edges must also be electrically connected to the driver chips. Currently, these interconnections are made by wire bonding, flex circuits or conductive adhesives. However, these methods pose serious limitations on the minimum spacing that can be achieved between individual tile elements in the matrix. The spacing between tiles represents a critical parameter that must be controlled in order to present a "seamless" look generated by the tiled LCD. More particularly, the dimension of the spacing between tiles should be less than the space between pixels in the LCD. One estimate for the tile-to-tile space is 380 microns. Of the 380 microns, only about 100 microns is available for passage of an interconnect from the tile edge to escaping or interconnecting circuitry of a tile carrier located below the tile.
However, employing flex circuits for this purpose requires a ledge of about 2000 to about 4000 microns. Likewise, employing conductive adhesive typically requires a ledge of at least about 2000 microns. Furthermore, conductive adhesives are limited in extendibility. Likewise, wire bonding presents a formable technical challenge because of the highly constrained workspace presented by a 100 micron ledge. Wire bonding is made even more difficult because two 180.degree. loops are needed to interconnect the necessary surfaces that oppose each other.
Accordingly, the desire is to move tiles closer together as performance and resolution are continuously being improved while the electronics is becoming smaller. Therefore, improved techniques for electrically interconnecting the LCD tiles to the underlying tile carriers that require significantly reduced real estate would be desirable.